Recent advances in LED (light emitting diodes) technology are revolutionizing the worldwide lighting industry by making possible the design of lighting arrangements that are more energy-efficient, longer-lasting, more durable, and more environmentally friendly than existing lighting technologies. LED lighting hence promises to become the major light source of the near future, not only to save energy, but also because the small size and the high efficiency of LEDs promote far more versatility of applications than did previous lighting technology. By mixing differently colored LEDs, any number of colors can be generated, with the color of the generated light being determined by the LEDs that are used as well as by the mixing ratios.
When it comes to lighting systems intended for street lighting, illumination of a preferably rectangular zone is desired, while consideration needs to be taken to regulations with regards to lighting uniformity, lighting intensity, glare and sky pollution. Traditionally, light sources such as high intensity discharge lamps e.g. sodium vapour lamps, fluorescent balloons or fluorescent tubes are commonly used. However, these kinds of light sources are quite bulky and hence vulnerable during windy weather conditions, and they require a frequent and time consuming maintenance. To meet these challenges, lighting system designs based on utilization of LEDs as sources of illumination have become an alternative approach.
The progress within LED technology has in turn stimulated the field of illumination optics, which previously related to lenses confined to such expensive niche application as stage lighting. A majority of illumination applications utilizes lenses that are circularly symmetric, enabling for a simplified design and mould-fabrication. Advances within the field, however, have resulted in new and improved ways to design illumination lenses that are not necessarily circularly symmetric. Modern injection-mould technology has full capability to fabricate arbitrary lens shapes, given their detailed mathematical description. Of the numerous illumination applications that have recently adapted LEDs as the light sources, many have lenses specifically designed for them.
One approach for a less bulky and more durable lighting arrangement implementing LEDs and such a specifically designed lens is for instance disclosed in EP2135005. In detail, EP2135005 presents an optical device having a lens for imparting a desired shape to a light beam, particularly relevant for lighting surfaces which have a great length with respect to their width, such as a road, a street or a motorway. With the disclosed lens, often quite bulky reflectors commonly arranged in the luminary head across the light path in order to direct the light beam with an appropriate angle toward e.g. the street, may be omitted.
However, even though EP2135005 provides an exemplary implementation of a lighting arrangement which may have a reduced thickness and hence be less bulky, there is still room for improvement with regards to compactness.